1. Field of the Invention
The present invention relates generally to scanning projection systems. More particularly, the present invention relates to an electronic shuttering system for a scanning projector system.
2. Related Art
There are a variety of visual projection systems and methods that use lasers to scan an image onto a projection screen. One of these methods involves scanning a linear array to form an image using a grating light valve (GLV) to project a linear array on a screen. A GLV projection system can be used to produce an image on a flat screen, or can be used to produce a panoramic image on a curved screen.
One challenge presented by laser scanning projection systems is the potential danger of laser light. It is well known that eye damage can occur if laser light (above a certain level) remains on an individual's retina beyond a certain amount of time. Where a scanning system is continuously scanning a laser across a large display area to produce an image, the laser energy is diffused, and thus may not present a hazard if it contacts an individual's retina while the scanning system is operating. However, if the scanning device malfunctions and stops, allowing a single stationary concentrated beam of light to leave the projector, this could be very damaging if the beam contacts the individual's eye. Human reaction time to intense light is usually on the order of about ¼ second. That is, it normally takes a person about ¼ second to blink or look away when intense light strikes the eye. However, laser light can easily damage the eye in far less time.
To prevent eye damage, there are a variety of laser safety systems that have been developed. Many of these comprise mechanical shutter or mirror systems that are configured to shutter or deflect a light source in case of a malfunction of a scanning projector. Some of these systems employ micromechanical optical switches, which move in response to electronic signals to reorient a very small mirror to redirect laser light. Unfortunately, mechanical shutters, even micromechanical ones, lack the speed needed to block laser light fast enough to eliminate all possibility of hazard in case of slow down or stoppage of a scanning laser system. Consequently, many mechanical shutter systems that are known only apply to conventional projector light sources (i.e. light produced from a bulb), and not laser light.
Light-steering devices are also known. However, prior systems known in the art do not provide a satisfactory method of stopping or controlling laser light from causing eye damage.